Micro-cantilever sensors are being developed to measure gas composition, concentrations, humidity, pressure and other parameters. Such sensor elements may be provided with a coating which will absorb the gas, causing the sensor to deflect and to change its mass or spring constant in such deflection. An accurate way of measuring such deflection is through measurement of the cantilever's natural resonant frequency. Changes in mass or spring constant cause a change in this natural resonant frequency which can be measured with a high degree of accuracy and sensitivity.
There has not been, however, a low-cost, automatic method of measuring the natural resonant frequency of a micro-cantilevered body. Such bodies are typically fabricated in a monolithic structure resembling an integrated circuit chip. One possible technique involves manually tuning an oscillator and looking for a peak amplitude with a lock-in amplifier. One drawback of this method is a frequency offset error that depends upon the Q of the cantilever. Another drawback is that this type of amplifier is deemed to be too expensive. Another possible technique would utilize Fast Fourier Transform (FFT) computation to find the peak amplitude.